High voltage resistors



FIG. 10 Fla. u.' FIG. l2] f Oct. 25, 1960 R. P. KEELER in AL 2,958,061

HIGH VOLTAGE RESISTORS Filed March 18, 1957 /5 F IE. IS. FIG. 14.

JNVENTORS. Y RALPH PAUL Keane- 1 BY Lznm H. fRflN/(L/N, 28 24 28 ATTORMEX United States Patent O 2,958,061 HIGH VOLTAGE RESISTORS Ralph Paul Keeler, 2606 Spring St, Redwood City, Calif., :mllfLeroy H. Franklin, 427 Alicia Way, Los Altos,

Filed Mar. 18, 1957, Ser. No. 646,623

3 Claims. (Cl. 338-64) This invention relates to the electronic art and deals with the construction of a high voltage resistor.

In constructing high voltage resistors, one of the problems encountered is corona, together with the problem of dissipating the heat generated by the ressitant element. Other problems such as the enormous length of wire used and how to dispose it in a short space, also how to handle non-inductive and/or inductive windings in such long lengths of wire are some of the difficulties that occur in making high voltage resistors.

The primary object of the invention to be described hereinafter is the provision of a construction for high voltage resistor characterized by sectional construction lending itself particularly well to the construction of built up resistors of predetermined value having incorporated in the various parts of the unit means for suppressing corona efiects as well as dissipating heat generated by the resistant element.

Briefly stated, our invention consists of making a plurality of identical sections, each section supplying a predetermined amount of resistance in the form of resistant wire wound on a bobbin. The wire may be either noninductively or inductively wound for any purpose de sired. The bobbins are the essential part of a section that may suitably be mounted on a core with conducting spacers therebetween to form a continuous resistor element from end to end of the built up resistor. Between the bobbins and around the periphery of the junction therebetween, we place a corona shield to control the corona. These shields not only reduce and control the corona but they also act as heat dissipators and serve as a direct contact with a cooling medium such as oil, or air.

Another object of this invention is the provision of high voltage resistors that may be used in short space and will have a uniform voltage distribution from end to end.

It is also an object of this invention to provide a high voltage resistor wherein the total resistance may be changed by adding or subtracting standard sections of predetermined resistance values.

Other objects and advantages will become apparent as the description proceeds in conjunction with the drawing in which:

Fig. 1 is a side view of our resistor.

Fig. 2 is an end view of Fig. 1.

Fig. 3 is a view similar to Fig. 1 showing how the parts of the resistor are assembled.

Fig. 4 is an enlarged fragmentary section showing how the section fits together.

Fig. 5 is a greatly magnified section of the rim of the corona shield.

Fig. 6 is a sectional view of the corona shield, substantially normal size.

Fig. 7 is a side view of the corona shield.

Fig. 8 is a sectional view of the bobbin which forms the basis for each section.

Fig. 9 is a side view of the bobbin.

Fig. 10 is a sectional view of another form the corona shield may take.

Fig. 11 is a side view of the form of corona shield shown in Fig. 10.

Fig. 12 is a sectional view showing how the form of shield illustrated in Figs. 10 and 11 is used to make up a resistant unit.

Fig. 13 is a sectional view of the spacer, and

Fig. 14 is an elevation of the spacer unit.

Referring to the drawing, it can be seen, in Fig. 3, that the complete resistant unit when made up according to our specification comprises a core, generally designated 11 formed of suitable material such as plastic epoxy, fibre or glass tubing, or rod, and in some cases, as pointed out hereinafter, the core may be a metal rod or tube, together with terminal nuts generally designated 12 adapted to be mounted on the ends of the tube 11 in any suitable manner such as by threads 13. It is to be understood that each end of the tube is supplied with such threads and that when the unit is complete the nuts 'on each end serve to compress the sections together on the core and form a continuous contact therethrough, and are also used to make contact in a circuit at each end of the unit. As shown next to the nut 12, we provide a spacer 14 which is adapted to I slidably fit over the core 11 and engage the nut 12 when the units are compressed together. In Figs. 13 and 14- we have shown such a spacer. Here it will be observed the spacer has flattened edges 15 the purpose of which will become apparent later. The spacer is made of sufficient thickness to work in connection with the corona shield as will be explained later and is formed of good conducting material. It will be noted that the spacers are used between all the parts that are placed on the core. The corona shield, generally designated 16, is best shown in Figs. 5, 6 and 7. Here it can be seen the shield is in the form of a ring that is shaped to form a bead on the outer periphery of the ring. In Fig. 5, we have shown a preferred form of the head. It has been greatly magnified here to bring out the important features of the bead. As shown, the outer edge of the shield 16 is made into a smooth round surface 17 which could be struck from a radius, and the corners 18 are also each rounded to give the exposure area of the shield a smooth rounded surface with no rough points or burrs. Extending inwardly from the head on the periphery is a short flange 19 which is of sufficient length to extend between the outer rim of the bobbin and should be of substantially the same thickness as the spacer 14 since a spacer is placed each side of the bobbin when assembled.

The next unit is a bobbin, generally designated 20. This unit is best shown in Figs. 8 and 9. Here it will be seen the bobbin is formed with a body 21 having a bore 22 adapted to slidably fit over the core 11. On the outer edge of the bobbin we form a channel or slot 23 adapted to receive windings 24 forming the resistive element. On each side of the bobbin there is provided a sheet of conducting material 25 such as copper or the like which is attached thereto in any suitable manner as by adhesion. The ends of the wire forming the resistant coils are brought out through holes 26 passing through the side walls of the channel 23 of the bobbin and are attached to the conducting sheets of material 25 each side by soldering 27. The winding 24 is predetermined and the value of the resistance on each bobbin may be standardized so that the number of units determines the total resistance. They may also be made inductive or non-inductive at the time of winding and in case of a capacity-resistive voltage divider for high frequency use, the shunt and series capacitance can be controlled by varying the series capacitance of each winding, taking into consideration the dimension of the coil and the dielectric constant of the material used in the coil form.

In Figs. 10, 1.1, and 12, we have shown another form of corona shield. This form may be used in place of the one shown in Figs. 6 and 7 without any change in dimension of any of the other parts. It. will be noted that this shield has a peripherial head 28 with an inwardly extending flange 29, which corresponds to the flange 19 on the shield 16 of Fig. 5, the only difference being that the bead is farther away from the outer edge of the coil thereby removing the corona shield farther away from the coil and allowing more surface area for dissipating the heat from the coils. The shields, in this form, act as fins for dissipating heat as well as shielding the coils and conductors from losses due to corona.

The type of construction shown by this invention is also useful in making convenient, compact, multi-sectional delay lines and pulse forming networks. For this purpose, the bobbins are made of high dielectric material, such as high dielectric constant ceramic, and are all inductively wound. The core instead of being dielectric as in the case of the high voltage resistor, would be made of metal. In all other respects, the parts are the same.

In assembling a resistor for a specified purpose, the amount of resistance is noted and supplied by adding. sections to each other until the combined total of the sections equals the resistance needed. We contemplate making some of our standard sections carry one megohm each and since one hundred or more of these sections may be mounted on a single core, it becomes evident a very high resistance may be mounted in a very small space.

In mounting our sections, the steps would appear somewhat as shown in Fig. 3. After the desired number of sections were in place they would be pressed together as shown in Fig. 1 by the nuts 12, using a spanner wrench or the like in holes 29 in the nuts. This would be the final form in which the resistor would be used. To change the overall resistance, it is merely a matter of adding or subtracting sections.

A resistor of the foregoing construction will find usefulness in fields wherever resistance may be needed in handling extremely high voltage or high power, and provides an improved mounting means for resistors of this type as well as a novel corona shield for controlling 4 corona. In addition, the structure provides a uniform voltage drop along the length of the resistor and an eflicient means for dissipating the heat generated by the resistant element. The usefulness of the construction will also be found to extend into the field of delay lines and pulse forming networks where it may be used to good advantage.

We claim: 7

1. An electrical unit comprising a supporting core, a plurality of bobbins slidably mounted on said core, said bobbins each having a conducting element thereon, a corona shield having a peripheral bead thereon of greater diameter than said bobbins mounted between said bobbins, and means for pressing said plurality of bobbins and shield together to form a continuous electrical conducting path through said elements and said shields.

2. The elements of claim 1 and in addition thereto, means for applying pressure to said bobbins and shields at each end of said core, said means including nuts screw.

threadedly mounted on the end of saidv core, wherein said nuts have smooth rounded exterior surfaces adapted to reduce corona. effects and form suitable electrical contactors. V I

3. In a high voltage resistor, a tubular supporting insulating core, a plurality of bobbins slidably mounted on said core, said bobbins having a peripheral channel for carrying a resistive element and a sheet of conducting material on each side thereof with means for conducting the opposite ends of said resistive element to their respective sheets, a corona shield having a periph:

eral bead thereon and an inwardly extending flange adapted to extend between said sheets and form a continuous electrical path through said plurality of bobbins and said shields when pressure is applied thereto at opposite ends of the core.

References Cited in the file of this patent UNITED STATES PATENTS 1,609,735 Rabezzana Dec. 7, 1926 2,067,967 Kniepen Jan. 19, 1937 2,407,171 McFarren Sept. 3, 1946 FOREIGN PATENTS I 612,165 Great Britain -1 Nov. 9, 1948 657,421 France May 22, 1929 940,438 France Dec. 13, 1948 

